This invention relates to a high strength frame coupling together two members and, more particularly, to a high strength push arm assembly connecting a tractor to a bulldozer blade.
Conventional bulldozers include push arms connected at one end to a tractor and at another end to a blade. The push arms are usually heavy, hollow beams extending from a hinged connection on the tractor to the bottom of the blade. These arms push the blade into the ground for digging or pushing the dirt. In one type of bulldozer, the blade is tiltable by use of a hydraulic jack or tilt cylinder which imparts a raising or lowering motion to one end of the blade relative to the other, thereby giving the blade what is known as tilt. Typically, the hydraulic jack is connected at one end to a bracket which is supported on a push arm and at the other end to the blade. Additionally, a tilt brace is connected to the blade and a second bracket which is supported on a second push arm to hold the blade in a tilted or upright position.
In view of the high forces acting on the push arm when the dirt is being moved, the push arms must be very strong to absorb these forces without fracturing or breaking. In one example, the push arm can be composed of a single piece which has the advantage of being relatively strong; however, such single piece construction is relatively expensive to manufacture. Consequently, use is also made of a push arm having two C-shaped plates which are welded together to form a box channel. The two C-shaped plates typically are welded together at the upper and lower surfaces of the push arm, with the brackets for the tilt cylinder and tilt brace being welded on this top surface. While this two-piece push arm construction is less expensive to manufacture than the single-piece construction, failures have been encountered and have been analyzed as resulting from the concentration of stresses at the top and bottom surfaces of the push arms where the welds are made. Consequently, it has been a problem to employ a push arm which is both inexpensive to manufacture and of high strength.